1. Technical Field
The present invention relates to wafer handling apparatus and method and, more particularly, to such apparatus and method for handling semiconductor wafers exhibiting significant bow.
2. Description of the Prior Art
During the processing of semiconductor wafers, some wafers may begin to exhibit warpage in the form of wafer bow, either simple (uniformly convex), compound (skewed convex), or complex (a composite of concave and convex). In particular, dielectrically isolated (DI) wafers may exhibit bow as a result of various processes utilized in forming the relatively thick polysilicon support layer (often referred to as a "handle"). In subsequent processing operations, the wafers must often be transferred individually between a carrier and a vacuum chuck. A transfer member, often referred to as a "transfer arm" or "transfer finger", may be utilized to perform this task. In general, a transfer arm is attached to a selected wafer by a vacuum through a relatively large opening in the surface of the arm. An O-ring may surround the opening to cushion the attachment and attempt to provide a vacuum seal. When utilized with wafers exhibiting significant bow (e.g., bow exceeding approximately 8 mils), an operator may be required to assist in the attachment, by forcing the wafer to lie flat against the transfer arm. This process obviously has the potential to damage the wafer surface or, in the extreme, result in breaking the wafer.
Therefore, a need remains for an improved method and apparatus for facilitating the transfer of bowed wafers.